Alloy steel



Patented Aug. 27, 1940v ALLOY STEEL Ralph P. De Vries, Menands, N. Y., assignor to Allegheny Ludlum Steel Corporation, Pittsburgh, Pa., 'a corporation of Pennsylvania N Drawing.

1939, Serial No. 250,187.

Original application January 10,

Divided and this application May'27, 1939, Serial No. 276,164

3 Claims.

My invention relates to alloy steels which substantially maintain their hardness when repeatedly heated to temperatures of the order of 1200 to 1600 F., and air cooled. It also relates to steels which are characterized by high hardness and high strength at elevated temperatures.

One of the objects of my invention is to provide an alloy steel which, while adapted for general use, is particularly suited for those applications where resistance to scaling combined with high strength and hardness at elevated temperatures are required characteristics, and where such strength and hardness are not substantially affected by repeated heating and cooling. Such and sulphur may be present in the usual small quantities, and the content thereof may even be raised to as high as about 0.15%, in which case the phosphorus increases the hardness .obtainable. Where phosphorus is present in more than the usual maximum of about 0.04%, small quantities of selenium, up to about 0.20%, may be added to improve the machineability of the alloy.

Below, 'I have set forth two specimens of my alloy steels together with their hardness in the as forged condition, their hardness when air cooled from temperatures of the order of 1200 F. to 1600 F., and their hardness after reheating steels are especially adapted for use in poppet and air cooling from temperatures of this order.

Analysis Cone rockwell hardness After reheating and air Melt No. 7 AS All cooled from cooling 0 Cr Mn N Go forged 1200 F. 140mm 1600 F. 1200 F. 1400 F. 1600;F.

s-47 .61 23.34 4.52 .26 .74 40/41 42 42 43 4o 40 4s s-72 .55 x37 4.15 .24 .36 3s 39 40 41 34 35 37 valves of internal combustion engines, hot work dies and similar articles which may be either forged or cast.

The alloying elements in my steel and the approximate percentage ranges, by weight, within which they are used to accomplish the foregoing objects are about as follows:

I Per cent C .50 to 1.25 Cr 20.00 to' 26.00 Mn 2.00 to 6.00 Co .25 to 2.50 N .10 to .50 Fe Balance -to 1600 F. The cobalt increases, in degree, the

maintainable hardness, and therefore makes the steel particularly useful for hot die purposes and also for poppet valve applications. Phosphorus It has often been found that steels which have a relatively high hardness when tested at room temperatures do not have relatively high strength or hardness when tested at elevated temperatures. high maintainable hardness in the temperature range of 1200 to 1600 F., has however, both high hardness and high strength at heat, the strength at a temperature of 1500 F. running consistently from 25,000 to 35,000 pounds per square inch. Such high strengths are usually found only in steels where high melting point and expensive elements such as molybdenum, tungsten or tantalum are used in fairly large proportions or where, in addition to thechromium', at least 10% to 20% of iron is replaced by nickel or manganese so that the alloy content approximates The steel of my invention which has a.

It also seems preferable when chromium is present in the extreme upper portion of its range, that both carbon and nitrogen should also be application Serial No. 250,187, filed January 10, 1939.

. What I claim is:

1. An alloy steel characterized by the substantial maintenance of hardness upon repeated heating to temperatures of the order of 1200 to 1600 F., and air cooling; said steel containing a plurality of ingredients of which the following, in the proportions stated, are the only elements necessary to attain said characteristic, carbon from 0.50% to 1.25%, chromium from 20% to 26%, manganese from 2% to 6%, nitrogen from 0.10% to 0.50%, cobalt from 0.25%. to 2.5%, and the balance iron.

2. An alloy steel characterized by the substantial maintenance of hardness upon repeated the balance iron.

heating to temperatures of the order of 1200" to 1600 F., and air cooling; said steel containing a .plurality of. ingredients of which the following, in the proportions stated, are the only elements necessary to attain said characteristic, carbon from 0.60% to 1.25%, chromium from 21.5% to 24.5%, manganese from 2.5% to 4.5%,nitrogen from 0.25% to 0.50%, cobalt from 0.25% to 2.5%, and the balance iron.

3. An alloy steel characterized by the substan-- tial maintenance of hardness upon'repeated heating to temperatures of the order of 1200 to 1600 F., and air cooling; said steel containing a plurality of ingredients of which the following, in the proportions stated, are the only elements necessary to attain said characteristic, carbon from 0.60% to 1.25%, chromium from 21% to 26%, manganese from 2% .to 4%, nitrogen from 0.25% to 0.50%, cobalt from 0.25% to 2.5%, and

RALPH P. Dr; yarns. 

